Nested PCR increases the efficiency of E6 amplicon synthesis. Examples of amplifications from HPV16-positive cervical scrapings by direct and nested PCR. (A) E6-1 amplification from cervical DNA by direct PCR with the LCRS/E7AS primer pair. Lane 1, 100 bp ladder. Lanes 2–5, DNA of cervical samples. Lane 6, Positive control 1 (pHPV16). Lane 7, Positive control 2 (pHPV18). Lane 8, Negative control (water). (B) E6-2 amplification by nested PCR with the E6F/PU-2R16 primer pair from direct PCR mixtures. Lanes 1–4, Amplicons generated using direct PCR mixtures from Panel A lanes 2–5 as templates. Lane 5, Positive control 1 (pHPV16). Lane 6, Positive control 2 (pHPV18). Lane 7, Negative control (water). Lane 8, 100 bp ladder.